With the rapid development of the ultra large scale integration (ULSI), the manufacturing process of integrated circuits (ICs) has become more and more complex and precise. Thus, stripe structures, such as poly silicon gates, and interconnect metal lines, etc., have become thinner and thinner; and the distance between stripe structures have become smaller and smaller as well. Therefore, it has become more and more difficult to form stripe structures which match the desired technology requirements using dry etching processes.
A process for forming stripe structures normally includes forming a patterned photoresist layer with stripe patterns by exposing a photoresist layer using a photomask having the stripe patterns; and followed by etching the to-be-etched layer by a dry etching process using the patterned photoresist layer as an etching mask. During the dry etching process, because the corner angles of the stripe structures are relatively thin; and they may be overly etched, the corner angles are easy to turn into arcs. In order to overcome the overly etching issues, a double-patterning method using double-lithography and double-etching has been developed.
FIGS. 1˜3 illustrate the method using the double-lithography and double-etching scheme. FIG. 1 illustrates a mask for the first lithography; FIG. 2 illustrates a mask for the second lithography; and the FIG. 3 illustrates the stripe structures formed by the method.
Specifically, a photoresist layer is formed on the to-be-etched layer firstly; and then the first lithography process is performed to expose and develop the photoresist layer using the mask illustrated in FIG. 1. Then, a first etching process is performed onto the to-be-etched layer using the patterned photoresist layer as an etching mask. After the first etching process, a second photoresist layer is formed on the to-be-etched layer which has been etched by the first etching process; and performing the second photolithography process to expose and develop the second photoresist layer using the mask illustrated in FIG. 2. Then, the to-be-etched layer etched by the first etching process is etched by a second etching process one more time; and stripe structures illustrated in FIG. 3 are formed. Because the stripe structures are formed by two etching processes, the shape of the corner angles of the formed stripe structures may match the desired requirements.
However, with continuously decreasing the critical dimension of the semiconductor processes, a distance between the end points of a stripe structure 1 and a stripe structure 2 which are in a same line is correspondingly shrunk. Thus, the difficulties for photolithography processes are increased; and the morphology of the sidewalls at ends of the stripe structure 1 and the stripe structure 2 may not match the desired requirements. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.